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Example 1:. F ind f(3) for function f, where. Evaluating a Function. Given a function y = f(x), we are often interested in finding function values for a given x. One example would be to find ordered pairs for points on the graph of the function.
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Example 1: Find f(3) for function f, where Evaluating a Function • Given a function y = f(x), we are often interested in finding function values for a given x. One example would be to find ordered pairs for points on the graph of the function. • To find just one function value, the simplest way is to substitute 3 for x in the Home Screen.
Example 2: Evaluate the function where x = 3/4. Evaluating a Function • If the value of x is more difficult that a simple integer, the Store function is very useful. (1) Enter 3/4 and press STO (2) Press x and then press ENTER. Slide 2
Now repeat the steps of example 1, using x in place of the value. Evaluating a Function • The value of .75 or 3/4 is now stored in the variable x. • If a fractional form is desired, press MATH and ENTER to select fraction, or Frac. • The press ENTER again. • The fractional form can be completed in one step. Slide 3
Example 3: Find f(7) for function f, where Evaluating a Function • A third way to evaluate a function is given in the next example. • Enter function f into Y1. Slide 4
Evaluating a Function • Use QUIT to get to the home screen. Then press VARS to get Variables. • Use the right arrow to highlight Y-VARS at the top of the screen, and press ENTER. • Press ENTER again to paste Y1 into the Home Screen. • Now type “(7)” and press ENTER. The result is f(7), the original problem to be solved. Slide 5
Evaluating a Function • The evaluation is in approximate decimal form. To find the exact value, use MATH|Frac. • Two other ways to evaluate a function are TABLE and TRACE, which are described in other modules. They will always give the function value in terms of a decimal, which may be rounded. • Thus, one of the most valuable aspects of Y1( ) is the ability to find exact function values (when x is rational). Slide 6